The present invention relates generally to medical compositions and methods, and more particularly to certain disinfectant/antimicrobial preparations and methods for using such preparations i) to disinfect articles or surfaces, ii) as a topical antiseptic for application to body parts, and iii) to prevent or deter scar formation and iv) to treat dermatological disorders such as wounds, burns, ulcers, psoriasis, acne and other scar forming lesions.
The prior art has included numerous antimicrobial agents which have purportedly been useable for disinfection of various articles and/or for topical application to a living being for antisepsis and/or treatment of dermal disorders (e.g., wounds, burns, abrasions, infections) wherein it is desirable to prevent or deter microbial growth to aid in healing. Such topical antimicrobial agents have contained a variety of active microbicidal ingredients such as iodine, mercurochrome, hydrogen peroxide, and chlorine dioxide.
Chlorite, a precursor of chlorine dioxide, is known to be useable as a disinfectant for drinking water and as a preservative for contact lens care solutions. However, chlorite exhibits only weak microbicidal activity within a concentration range that is acceptable and safe for topical application to the skin (e.g., 200-1000 parts per million). Thus, chlorite has not been routinely used as an active microbicidal ingredient in preparations for topical application to the skin.
In view of the limited usefulness of chlorite as an antiseptic or topical microbicide, various compositions and methods have been proposed for activation or enhancement of the microbicidal activity of chlorite. Examples of such compositions and methods for activation or enhancement of the microbicidal activity of chlorite are described in U.S. Pat. No. 4,997,616 (describing general activation); U.S. Pat. No. 5,279,673 (describing acid activation) and U.S. Pat. No. 5,246,662 (describing transitional metal activation).
Chlorine dioxide (ClO2) and xe2x80x9cstabilized chlorine dioxidexe2x80x9d are known to be useable as antiseptics. Chemically, chlorine dioxide is an oxidizing agent which has strong microbicidal activity. Chlorine dioxide is generally regarded as superior even to gaseous chlorine, in certain water treatment applications where it is used as to eliminate algae and other organic material and/or to remove odors or tastes. Chlorine dioxide is also effective as a microbicide, for elimination of bacteria, viruses, and microbial spores.
In addition to its use as a microbicide, chlorine dioxide is a highly reactive, unstable radical which is useable as an oxidizing agent in a number of other chemical and biochemical applications. For example, as described in U.S. Pat. No. 4,855,135, chlorine dioxide can be used for (a) oxidation of double bonds between two carbon atoms; (b) oxidation of unsaturated fatty acids (lipids) via double bonds between two carbon atoms; (c) acceleration of hydrolysis of carboxylic anhydrides; (d) oxidation of aldehydes to the corresponding carboxylic acids; (e) oxidation of alcohols; (f) oxidation of amines; (g) oxidation of phenols, phenolic derivatives and thiophenolic compounds; (h) moderate oxidation of hydroquinones; (i) oxidation of amino acids, proteins and polyamides; (j) oxidation of nitrates and sulphides; and (k) alteration of the CHO and CH2OH radicals of carbohydrates to produce carboxylic functionality.
Concentrated chlorine dioxide in its liquid or gaseous state is highly explosive and poisonous. As a result, concentrated chlorine dioxide must be handled and transported with great caution. For this reason, it is generally not feasible to dispense pure chlorine dioxide for use as a topical antimicrobial agent or disinfectant. Instead, same antimicrobial or disinfectant preparations have been formulated to provide for xe2x80x9cacid generationxe2x80x9d of chlorine dioxide. Such acid generation solutions contain a metal chlorite (i.e., a precursor of chlorine dioxide available in powdered or liquid form) in combination with an acid which will react with the chlorite to liberate or release chlorine dioxide. Generally, any acid may be used for acid generation of chlorine dioxide, including strong acids such as hydrochloric acid and sulfuric acid and relatively weak acids such as citric and tartaric acid. Drawbacks or problems associated with these prior chlorine dioxide generating systems include a) the inconvenience of handing two separate containers or chemical components, b) the difficulty of delivering such two-component systems to the intended site of application, and c) the fact that these prior systems are of acid, rather than neutral, pH. Moreover, the prior chlorine dioxide generating systems which utilize acid-induced generation of chlorine dioxide can, if uncontrolled, cause the generation of chlorine dioxide to occur quite rapidly and, as a result, the disinfectant or antimicrobial potency of the solution may be short lived. Increasing the concentration of chlorite and acid within the solution may prolong its disinfectant or antimicrobial shelf life, but such increased concentrations of these chemicals can result in toxicities or (in topical applications) skin irritation. Such increased concentrations may also result in the generation of more chlorine dioxide than is required.
Various methods have been described to limit or control the rate at which chlorine dioxide is produced in xe2x80x9cacid generationxe2x80x9d solutions. For instance, U.S. Pat. No. Re. 31,779 (Alliger) describes a germicidal composition which comprises a water soluble chlorite, such as sodium chlorite, in combination with lactic acid. The particular composition possesses improved disinfectant properties, properties not attained by using the same composition but replacing the lactic acid with other acids such as phosphoric acid, acetic acid, sorbic acid, fumaric acid, sulfamic acid, succinic acid, boric acid, tannic acid, and citric acid. The germkilling composition is produced by contacting an acid material containing at least 15% by weight of lactic acid with sodium chlorite in aqueous media, the amount of lactic acid being sufficient to lower the pH of the aqueous media to less than about 7. The methods disclosed of disinfecting and sanitizing a germ-carrying substrate, such as skin, include either application of the germ-killing composition, or application of the reactants to provide in situ production thereof. Also, U.S. Pat. No. 5,384,134 (Kross) describes acid induced generation of chlorine dioxide from a metal chlorite wherein the chlorite concentration is limited by the amount of available chlorous acid. In particular, the Kross patent describes a method for treating dermal disorders wherein a first gel, which comprises a metal chlorite, is mixed with a second gel, which comprises a protic acid. The chlorite ions present in such solution as chlorous acid purportedly comprise no more than about 15% by weight of the total chlorite ion concentration in the composition, and the mixture of the two gels purportedly generates chlorine dioxide over an extended time of up to 24 hours.
Other prior patents have purported to describe the use of xe2x80x9cstabilizedxe2x80x9d chlorine dioxide as a means of chlorine dioxide generation. The term stabilized chlorine dioxide refers to various compositions in which the chlorine dioxide is believed to be held in solution in the form of a labile complex. The stabilization of chlorine dioxide by the use of perborates was disclosed in U.S. Pat. No. 2,701,781 (de Guevara). According to the de Guevara patent, an antiseptic solution of stabilized chlorine dioxide can be formed from an aqueous solution of chlorine dioxide and an inorganic boron compound with the boron compound and the chlorine dioxide being present in the solution as a labile complex. The chlorine dioxide, fixed in this stable condition, is an essential ingredient of the antiseptic solution. The de Guevara patent discloses that the chlorine dioxide may be introduced into the compositions either by in situ generation or it may be generated externally and introduced into the solution, as by bubbling the chlorine dioxide gas into the aqueous solution. Various methods may be employed for the external production of the chlorine dioxide, such as reaction of sulfuric acid with potassium chlorate or the reaction of the chlorate with moist oxalic acid. Alternatively, chlorine dioxide can be generated in situ by reaction of potassium chlorate and sulfuric acid. Note that whether the chlorine dioxide is produced in situ or externally, it is essentially an acid induced liberation of the chlorine dioxide from potassium chlorate.
U.S. Pat. No. 4,317,814 (Laso) describes stabilized chlorine dioxide preparations for treatment of burns in humans. Aqueous mixtures of perborate stabilized solutions of chlorine oxides, such as chlorine dioxide, in combination with glycerin are described for topical application to burned areas and may also be administered by oral application for treatment of burns. The aqueous solutions of perborate stabilized chlorine oxides are disclosed as being prepared by mixing with water the following: sodium chlorite, sodium hypochlorite, hydrochloric acid, sulfuric acid, an inorganic perborate, and a peroxy compound, such as sodium perborate. Thus, the solutions prepared in accordance with the Laso patent contain chlorine dioxide, hypochlorite and peroxy compounds as strong oxidizing agents and appear to utilize acid activation of the chlorine dioxide. The Laso patent states that the methods disclosed therein resulted in an immediate subsidence of burn related pain in many cases, that healing was rapid and characterized by an absence of infection or contraction, and that the burn scars were smooth and resembled normal tissue, thus eliminating the need for plastic surgery in certain cases. However, long term storage and stability are issues with the aqueous solutions described in the above-identified Laso patent, because such mixtures tend to generate chlorine dioxide very quickly, thus diminishing the long term stability of such mixtures.
U.S. Pat. No. 3,271,242 (McNicholas et al.) describes stabilized chlorine dioxide solutions which are formed by combining chlorine dioxide gas with an aqueous solution containing a peroxy compound, and subsequently heating the solution to a temperature which is high enough to drive off all free peroxide, but low enough not to destroy the chlorine dioxide. McNicholas et al. States that temperatures xe2x80x9cmuch belowxe2x80x9d 70 degrees C. are ineffective to drive of the free peroxide in the solution and that tempratures should not exceed 92 degrees C. because at higher temperatures the chlorine dioxide will be driven off. McNicholas further states that, although not xe2x80x9centirely understood,xe2x80x9d it was believed that heating of the solution to drive off free peroxide was necessary because any free hydrogen peroxide allowed to remain in the solution would act as a leaching agent to release the chlorine dioxide from the solution.
Antibiotic compounds have also been commonly used for the therapeutic treatment of burns, wounds and skin infections. While antibiotics may provide an effective form of treatment, several dangers are often associated with the use of antibiotics in the clinical environment. These dangers may include but are not limited to: (1) changes in the normal flora of the body, with resulting xe2x80x9csuperinfectionxe2x80x9d due to overgrowth of antibiotic resistant organisms; (2) direct antibiotic toxicity, particularly with prolonged use which can result in damage to kidneys, liver and neural tissue depending upon the type of antibiotic; (3) development of antibiotic resistant microbial populations which defy further treatment by antibiotics.
While even minor wounds and abscesses can be difficult to treat in certain patients and/or under certain conditions, there are well known dermal disorders such as psoriasis and dermal ulcerations, which present particular challenges for successful treatment.
Psoriasis is a noncontagious skin disorder that most commonly appears as inflamed swollen skin lesions covered with silvery white scale. This most common type of psoriasis is called xe2x80x9cplaque psoriasisxe2x80x9d. Psoriasis comes in many different variations and degrees of severity. Different types of psoriasis display characteristics such as pus-like blisters (pustular psoriasis), severe sloughing of the skin (erythrodermic psoriasis), drop-like dots (guttate psoriasis) and smooth inflamed lesions (inverse psoriasis).
The cause of psoriasis is not presently known, though it is generally accepted that it has a genetic component, and it has recently been established that it is an autoimmune skin disorder. Approximately one in three people report a family history of psoriasis, but there is no pattern of inheritance. There are many cases in which children with no apparent family history of the disease will develop psoriasis.
The occurrence of psoriasis in any individual may depend on some precipitating event or xe2x80x9ctrigger factor.xe2x80x9d Examples of xe2x80x9ctrigger factorsxe2x80x9d believed to affect the occurrence of psoriasis include systemic infections such as strep throat, injury to the skin (the Koebner phenomenon), vaccinations, certain medications, and intramuscular injections or oral steroid medications. Once something triggers a person""s genetic tendency to develop psoriasis, it is thought that in turn, the immune system triggers the excessive skin cell reproduction.
Skin cells are programmed to follow two possible programs: normal growth or wound healing. In a normal growth pattern, skin cells are created in the basal cell layer, and then move up through the epidermis to the stratum corneum, the outermost layer of the skin. Dead cells are shed from the skin at about the same rate as new cells are produced, maintaining a balance. This normal process takes about 28 days from cell birth to death. When skin is wounded, a wound healing program is triggered, also known as regenerative maturation. Cells are produced at a much faster rate, theoretically to replace and repair the wound. There is also an increased blood supply and localized inflammation. In many ways, psoriatic skin is similar to skin healing from a wound or reacting to a stimulus such as infection.
Lesional psoriasis is characterized by cell growth in the alternate growth program. Although there is no wound at a psoriatic lesion, skin cells (called xe2x80x9ckeratinocytesxe2x80x9d) behave as if there is. These keratinocytes switch from the normal growth program to regenerative maturation. Cells are created and pushed to the surface in as little as 2-4 days, and the skin cannot shed the cells fast enough. The excessive skin cells build up and form elevated, scaly lesions. The white scale (called xe2x80x9cplaquexe2x80x9d) that usually covers the lesion is composed of dead skin cells, and the redness of the lesion is caused by increased blood supply to the area of rapidly dividing skin cells.
Although there is no known cure for psoriasis, various treatments have been demonstrated to provide temporary relief in some patients. However, the effectiveness of the currently accepted treatments for psoriasis is subject to considerable individual variation. As a result, patients and their physicians may have to experiment and/or combine therapies in order to discover the regimen that is most effective. The currently available treatments for psoriasis are often administered in step-wise fashion. Step 1 treatments include a) topical medications (e.g., topical steroids, topical retinoids), b) systemic steroids, c) coal tar, d) anthralin, e) vitamin D3, and sunshine. Step 2 treatments include a) phototherapy (e.g, ultraviolet radiation), b) phochemotherapy (e.g., a combination of a topically applied radiation-activated agent followed by radiation to activate the agent) and c) combination therapy. Step 3 treatments include a) systemic drug therapies such as methotrexate, oral retinoids and cyclosporine and b) rotational therapy.
Dermal ulcerations are known to occur as a result of pressure, wear, or primary/secondary vascular disorders. Dermal ulcerations are generally classified according to their etiology, as follows:
a. Decubitus/Pressure Ulcers
A decubitus ulcer or pressure sore is a lesion caused by unrelieved pressure resulting in damage of the underlying tissue. Decubitus ulcers usually develop over a bony prominence such as the elbow or hip. The unrelieved pressure, along with numerous contributing factors, leads to the skin breakdown and persistent ulcerations.
b. Venous Ulcers
Venous ulcers may result from trauma or develop after chronic venous insufficiency (CVI). In CVI, venous valves don""t close completely, allowing blood to flow back from the deep venous system through the perforator veins into the superficialvenous system. Over time, the weight of this column of blood causes fluid and protein to exude into surrounding tissues, resulting in swollen, hyperpigmented ankles, tissue breakdown, and ulceration. Venous ulcers may be shallow or extend deep into muscle.
c. Arterial Ulcers
Leg ulcers also can develop in patients with arterial insufficiency caused by arterial vessel compression or obstruction, vessel wall changes, or chronic vasoconstriction. Smokers face an especially high risk of arterial disease because nicotine constricts arteries, encourages deposits of atherosclerotic plaque, and exacerbates inflammatory arterial disease (Buerger""s disease) and vasoconstrictive disease (Raynaud""s disease or phenomenon). Arterial ulcers, caused by trauma to an ischemic limb, can be very painful.
d. Diabetic Ulcers
Arterial insufficiency can be the cause of a nonhealing ulcer in a patient with diabetes. However, most diabetic ulcers result from diabetic neuropathyxe2x80x94because the patient can""t feel pain in his foot, he""s unaware of injuries, pressure from too-tight shoes, or repetitive stress that can lead to skin breakdown.
There remains a need in the art for the formulation and development of new disinfectants and topically applicable preparations for the treatment of dermal disorders, such as wounds, burns, abrasions, infections, ulcerations, psoriasis and acne.
The present invention provides antimicrobial preparations (e.g., solutions, gels, ointments, creams, etc.) for disinfection of articles or surfaces (e.g., contact lenses, counter tops, etc.), antisepsis of skin or other body parts, prevention or minimization of scarring, and/or treatment or prophylaxis of dermal (i.e., skin or mucous membrane) disorders (e.g., wounds, burns, infections, cold sores, ulcerations, psoriasis, scar forming lesions, acne). The antimicrobial preparations of this invention generally comprise from about 0.001% to about 0.10 by weight of a metal chlorite in combination with from 0.001% to 0.05% of a peroxy compound such as hydrogen peroxide. Additionally, the chlorite/peroxide preparations of the present invention may contain additional components such as polymeric lubricants and surfactants, and/or may be formulated in a polymeric drug delivery system or liposomal preparation. The chlorite/peroxide preparations of the present invention have broad antimicrobial activity, including for example activity against gram negative and gram positive bacteria, yeasts and fungi. Moreover, when applied or administered to treat dermal disorders (e.g., wounds, burns, infections, ulcerations, acne and psoriasis), the chlorite/peroxide preparations of the present invention will not only prevent or lessen microbial infection, but will additionally provide oxygen to the affected tissue, aid in healing and deter scar formation.
Further in accordance with the invention, there are provided methods for disinfection of items (e.g., contact lenses) and methods for treatment of dermal disorders (e.g., wounds, burns, infections, ulcerations and psoriasis) by application or administration of a chlorite/peroxide preparation of the present invention.
Further in accordance with the invention, there are provided methods for deterring scar formation by application or administration of a chlorite/peroxide preparation of the present invention.
Further aspects and objects of the present invention will become apparent to those of skill in the art upon reading and understanding of the following detailed description and the examples set forth therein.
The following detailed description and examples are provided for the purpose of describing certain exemplary embodiments of the invention only, and are not intended to limit the scope of the invention in any way.
The present invention provides preparations which contain chlorite (e.g., a metal chlorite) in combination with a small amount of hydrogen peroxide in neutral aqueous (pH 6.8-7.8, preferably pH 7.0-7.4) solution. These preparations exhibit synergistic antimicrobial activity without generating chlorine dioxide during storage, thereby rendering the stability of these solutions acceptable for pharmaceutical use. For example, an aqueous solution containing 400 ppm chlorite plus 100 ppm hydrogen peroxide remains stable beyond 18 months at room temperature, and is effective to reduce candida albicans activity by 1.0 log within a 6 hrs of challenge, even though the individual components of such solution are ineffective when applied separately at the same concentrations, to reduce candida albicans activity. Additionally, the hydrogen peroxide present within the chlorite/peroxide solutions of the present invention readily decomposes into molecular oxygen and water, upon contact with the peroxidase and catalase enzymes present in tissue and/or some body fluids. Such in situ generation of molecular oxygen contributes to cell vitality and enhances wound healing.
The chlorite/H2O2 solutions of the present invention are sufficiently stable to be formulated in combination with polymeric lubricants (non-ionic and/or anionic; e.g., HPMC, methylcellulose, CMC, etc.) and/or in combination with block polymer based surfactants (e.g., (Pluronic(trademark) surfactants. For example, an aqueous chlorite/hydrogen peroxide system can be formulated together with methocel as a lubricant and pluronics as a surfactant for contact lens disinfectant solution (viscosity up to 50 cps at 25 degrees C.) in an ophthalmically acceptable tonicity (e.g., osmolality of at least about 200 mOsmol/kg) and a buffer to maintain the pH of the formulation within an acceptable physiological range. The formulation of the contact lens disinfection solution contains chlorite preferably from about 0.03 to about 0.06 weight/volume percent and hydrogen peroxide preferably from about 0.0002 to about 0.05 weight/volume percent. Again, the presence of hydrogen peroxide provides the beneficial oxygen molecule to the cornea upon contact with catalase in the tear.
The chlorite/peroxide preparations of the present invention may be formulated in various ways, including liquid solutions, gels, ointments, creams, sprays, etc. Set forth herebelow are but a few examples of the types of specific formulations which may be prepared in accordance with this invention.
i. A Stable Chlorite/Peroxide Liquid Solution
The following Formula 1 is a presently preferred formulation of a liquid chlorite/peroxide solution of the present invention:
Sodium Chlorite . . . 0.02%-0.10%
Hydrogen Peroxide . . . 0.005%-0.01%
methylcellulose (Methocel A(trademark)) . . . 0.05%-0.2%
Boric Acid . . . 0.15%
Sodium Chloride . . . 0.75%
surfactant (Pluronic F-68(trademark)) . . . 0.1%
HCl or NaOH . . . Adjust pH 7.4
Purified water . . . Q.S. to volume
The chlorite/peroxide solutions of the present invention, such as the solution of the above-shown preferred formulation, may be used for a variety of medical and non-medical applications including but not necessarily limited to a) disinfection of articles and surfaces such as contact lenses, medical/dental instruments, counter tops, treatment tables, combs and brushes, etc; antisepsis of skin or body parts (e.g., a disinfectant hand wash, antiseptic facial scub, etc.) and b) treatment or prophylaxix of dermal (I.e., skin or mucous membrane) disorders such as wounds, burns, infections, ulcerations, cold sores, psoriasis, acne, and c) deterrence or prevention of scar formation.
As pointed out earlier, the chlorite/hydrogen peroxide system of the present invention is sufficiently stable to be formulated in a polymeric gel form or in a paste form. Furthermore, such polymeric gel or paste formulation can contain polymers which delay or control the release of the chlorite/hydrogen peroxide (e.g., a sustained release delivery system). Such sustained release formulations provide outstanding benefits of increasing therapeutic index by maintaining the effective concentration of chlorite/H202 for a prolonged time on the injured sites, by preventing the injured sites from external microbial contamination by forming a seal over the injured sites, and by providing oxygen molecule to the injured tissues. Unlike the conventional ointment, the polymeric gel provides a dry, clean, and comfortable coating on the injured sites upon application. Such gel formulations may contain polymeric drug delivery vehicles like hydroxypropyl methylcellulose (HPMC), methylcellulose (Methocel(trademark)), hydroxyethylcellulose (HEC), and carboxymethylcellulose (CMC), etc.
ii. A Stable Chlorite/Peroxide Gel
The following Formula 2 is a presently preferred formulation of a chlorite/peroxide gel of the present invention:
Sodium Chlorite . . . 0.02%-0.10%
Hydrogen Peroxide . . . 0.005%-0.01%
Methocel A . . . 2.0%
Boric Acid . . . 0.15%
Sodium Chloride . . . 0.75%
Pluronic F-68 . . . 0.1%
HCl or NaOH . . . Adjust pH 7.4
Purified water . . . Q.S. to volume
Any of the preparations of the present invention may be formulated for sustained release of the active components by forming liposomes of the preparing in accordance with well known liposomal forming techniques and/or by adding to the formulation a pharmaceutically acceptable and effective amount (e.g., typically 1-20 percent by weight) of a sustained release component such as a polymer matrix or one or more of the following:
a cellulose ester;
hydroxymethylpropyl cellulose;
methylhydroxyethyl cellulose;
hydroxypropyl cellulose;
hydroxyethyl cellulose;
carboxymethyl cellulose;
a salt of a cellulose ester;
cellulose acetate;
hydroxypropylmethyl cellulose phthalte;
methacrylic acid-methyl methacrylate copoymer;
methacrylic acid-ethyl acetate copolymer;
polyvinylpyrrolidone;
polyvinyl alcohol;
a phospholipid;
cholesterol;
a phospholipid having a neutral charge;
a phospholipid having a negative charge;
dipalmytoyl phoshatidyl choline;
dipalmytoyl phoshatidyl serine; and,
sodium salts thereof.